Fluorinated diene compound and fluoropolymer, and methods for their production

ABSTRACT

A novel fluoropolymer which can be an optical resin material having a low refractive index and excellent heat resistance, and a novel fluorinated diene compound having two unsaturated bonds, capable of presenting such a fluoropolymer, are presented. Further, by virtue of the low refractive index and excellent heat resistance, the polymer presents a high performance optical transmitter and a plastic optical fiber.  
     A fluorinated diene compound represented by CF 2 ═CFCF(OR f )CF 2 OCF═CF 2  (wherein R f  is a perfluoroalkyl group such as a trifluoromethyl group), and a fluoropolymer thereof. Further, an optical transmitter made by using such a fluoropolymer, and a plastic optical fiber having a core comprising such a fluoropolymer and a fluorinated low molecular compound contained therein as a refractive index-increasing agent.

TECHNICAL FIELD

The present invention relates to a fluorinated diene compound having twounsaturated bonds, and a method for its production, as well as afluoropolymer, a fluoropolymer solution employing it, an opticaltransmitter and a plastic optical fiber.

BACKGROUND ART

As a fluorinated diene compound having two carbon-carbon unsaturateddouble bonds (hereinafter referred to as unsaturated bonds),CF₂═CF(CF₂)_(k)OCF═CF₂ (wherein k is an integer of from 1 to 3) is known(JP-A-1-143843). By cyclopolymerization of this compound, it is possibleto obtain an amorphous polymer. Such a polymer has high elastic modulus,yield and breaking elongation and is tough and excellent also in impactresistance. Further, it has high transparency, and it is useful for anoptical material for e.g. optical fibers and optical waveguides.However, the optical material employing this polymer has a low glasstransition temperature (T_(g)) and thus has a drawback that the opticalcharacteristics are likely to change when it is used at a hightemperature for a long period of time. Accordingly, it is desired todevelop a material having a higher T_(g).

It is an object of the present invention to provide a novel polymerwhich not only maintains the mechanical properties which theabove-mentioned amorphous polymer has, but also has a higher glasstransition temperature, so that it can be an optical resin materialhaving a low refractive index and being excellent in heat resistance,and a novel fluorinated diene compound having two unsaturated bonds,which presents such a polymer. Further, it is an object of the presentinvention to provide a high performance light transmitter and a plasticoptical fiber, which have a low refractive index and excellent heatresistance.

DISCLOSURE OF THE INVENTION

As a result of an extensive study, the present inventors have produced anew specific fluorinated diene compound and further have found itpossible to accomplish the above objects by polymerizing thisfluorinated diene compound. That is, the present invention provides thefollowing:

1. A fluorinated diene compound represented by the following formula(1):CF₂═CFCF(OR^(f))CF₂OCF═CF₂  (1)wherein R^(f) is a perfluoroalkyl group.

2. The fluorinated diene compound, wherein R^(f) is a trifluoromethylgroup.

3. A method for producing a fluorinated diene compound represented bythe following formula (1), characterized in that a dehalogenationreaction is carried out at halogen atoms other than fluorine atoms in atleast one compound selected from a compound represented by the followingformula (2) and a compound represented by the following formula (3):CF₂═CFCF(OR^(f))CF₂OCF═CF₂  (1)CF₂Z¹CFZ²CF(OR^(f))CF₂OCF═CF₂  (2)CF₂Z¹CFZ²CF(OR^(f))CF₂OCFZ³CF₂Z⁴  (3)wherein R^(f) is a perfluoroalkyl group, and each of Z¹, Z², Z³ and Z⁴which are independent of one another, is a halogen atom other than afluorine atom.

4. A fluoropolymer comprising monomer units formed bycyclopolymerization of a fluorinated diene compound represented by theformula (1), or monomer units formed by cyclopolymerization of afluorinated diene compound represented by the formula (1) and monomerunits formed by polymerization of other monomer polymerizable with thefluorinated diene compound represented by the formula (1):CF₂═CFCF(OR^(f))CF₂OCF═CF₂  (1)wherein R^(f) is a perfluoroalkyl group.

5. The fluoropolymer, wherein R^(f) is a trifluoromethyl group.

6. The fluoropolymer, wherein the monomer units formed by thecyclopolymerization of the fluorinated diene monomer represented by theformula (1), are monomer units represented by any one of the followingformulae, wherein R^(f) is as defined above:

7. The fluoropolymer, wherein the monomer units of other polymerizablemonomer are monomer units formed by polymerization of at least onemember selected from a fluorinated diene which is cyclopolymerizable,other than the fluorinated diene compound represented by the formula(1), a monomer having a fluorinated aliphatic cyclic structure, afluorinated non-cyclic vinyl ether monomer and a fluoroolefin.

8. The fluoropolymer, wherein the other monomer units are monomer unitsformed by polymerization of at least one member selected fromtetrafluoroethylene, perfluoro(butenyl vinyl ether) andperfluoro(2,2-dimethyl-1,3-dioxole).

9. A fluoropolymer solution having the fluoropolymer dissolved in atleast one fluorocarbon solvent selected fromperfluoro(2-butyltetrahydrofuran), perfluorooctane, perfluorohexane,perfluoro(tributylamine), perfluoro(tripropylamine), perfluorobenzeneand dichloropentafluoropropane.

10. An optical transmitter made by using the fluoropolymer.

11. A plastic optical fiber having a core formed of a mixture comprisingthe fluoropolymer and a fluorinated low molecular compound as arefractive index-increasing agent.

12. The plastic optical fiber, wherein the fluorinated low molecularcompound is at least one compound selected fromperfluoro(triphenyltriazine), perfluoro(1,3,5-triphenylbenzene) and achlorotrifluoroethylene oligomer.

13. The plastic optical fiber, wherein the plastic optical fiber is arefractive index distribution type optical fiber.

BEST MODE FOR CARRYING OUT THE INVENTION

The fluorinated diene compound of the present invention is a compoundrepresented by the formula (1) (hereinafter, the compound represented bythe formula (1) may be referred to also as the compound (1), andcompounds represented by other formulae may likewise be referred to.).In the formulae, R^(f) represents a perfluoroalkyl group.

The perfluoroalkyl group (hereinafter, the perfluoroalkyl group may bereferred to as a R^(f) group) is a group having all of hydrogen atoms ofan alkyl group substituted by fluorine atoms. The structure of the R^(f)group may, for example, be a linear structure, a branched structure, acyclic structure or a structure having a partially cyclic structure.

As the R^(f) group having a linear structure, a R^(f) group having from1 to 8 carbon atoms, is preferred, and it may, for example, be —CF₃,—CF₂CF₃, -nC₃F₇, -nC₄F₉, -nC₅F₁₁, -nC₆F₁₃, -nC₇F₁₅ or -nC₈F₁₇, andparticularly preferred is —CF₃.

As the R^(f) group having a branched structure, —CF(CF₃)₂, -isoC₄F₉,-secC₄F₉ or -tertC₄F₉ may, for example, be mentioned.

As R^(f) having a cyclic structure (i.e. a perfluorocycloalkyl group), aperfluorocyclopropyl group, a perfluorocyclobutyl group, aperfluorocyclopentyl group, a perfluorocyclohexyl group or a grouphaving a perfluoroalkyl group having a linear structure or branchedstructure bonded to a carbon atom constituting the ring of such a group,may be mentioned.

As the R^(f) group having a partially cyclic structure, a group havingperfluorinated an alkyl group having a linear structure substituted by acycloalkyl group, or a group having perfluorinated an alkyl group havinga branched structure substituted by a cycloalkyl group may be mentioned,and, for example, a perfluoro(cyclohexylmethyl) group or aperfluoro(cyclohexylethyl) group is preferred.

R^(f) in the compound (1) of the present invention is particularlypreferably a trifluoromethyl group.

The following compounds may be mentioned as specific examples of thecompound (1) of the present invention.CF₂═CFCF(OCF₃)CF₂CF═CF₂CF₂═CFCF(OCF₂CF₃) CF₂OCF═CF₂CF₂═CFCF(OCF₂CF₂CF₃)CF₂OCF═CF₂CF₂═CFCF(OCF₂ CF₂CF₂CF₃)CF₂OCF═CF₂CF₂═CFCF(OCF(CF₃)₂)CF₂OCF═CF₂CF₂═CFCF(OCF₂CF(CF₃)₂)CF₂OCF═CF₂CF₂═CFCF (OC(CF₃)₃)CF₂OCF═CF₂

The fluorinated diene compound of the present invention is preferablyproduced by a method wherein a dehalogenation reaction is carried out athalogen atoms other than fluorine atoms in at least one compoundselected from a compound represented by the following formula (2) and acompound represented by the following formula (3):CF₂Z¹CFZ²CF(OR^(f))CF₂OCF═CF₂   (2)CF₂Z¹CFZ²CF(OR^(f))CF₂OCFZ³CF₂Z⁴   (3)

In the above formulae, R^(f) is a perfluoroalkyl group corresponding toR^(f) in the formula (1).

Further, each of Z¹, Z², Z³ and Z⁴ which are independent of one another,is a halogen atom other than a fluorine atom, and may, for example, be achlorine atom, a bromine atom or an iodine atom, preferably a chlorineatom or a bromine atom, particularly preferably each being a chlorineatom. By the dehalogenation of such halogen atoms, a double bond will beformed, whereby a fluorinated diene compound represented by the formula(1) will be formed.

The dehalogenation in the method for producing a fluorinated dienecompound of the present invention, is preferably carried out by having adehalogenating agent reacted in a polar solvent. The dehalogenatingagent is a reactive agent which reacts with halogen atoms in a substrateto withdraw the halogen atoms. Such a dehalogenating agent may, forexample, be zinc, sodium, magnesium, tin, copper, iron or other metals.Zinc is particularly preferred from the viewpoint of such a reactioncondition that a relatively low reaction temperature can be therebyemployed.

As the polar solvent, an organic polar solvent such asdimethylformamide, 1,4-dioxane, diglime or methanol, or water, ispreferred.

The amount of the dehalogenating agent is preferably from 1 to 20 timesby mol, particularly preferably from 1 to 10 times by mol, especiallypreferably from 2 to 10 times by mol, based on the total amount of thecompound (2) and/or the compound (3) to be used for the reaction. Thereaction temperature is usually from 40 to 100° C., preferably from 50to 80° C. The dehalogenation reaction is usually carried out by dropwiseadding the compound (2) in the presence of the dehalogenating agent andthe solvent. Isolation of the reaction product is preferably carried outby withdrawing the reaction product from the reaction system quicklyafter the reaction, by reactive distillation.

As a preferred embodiment of the compound (2) herein R^(f) is atrifluoromethyl group and each of Z¹ and Z² is a chlorine atom, thefollowing compound (2-1) can be obtained by pyrolyzing the compound(2-2). This compound (2-2) can be synthesized by addinghexafluoropropylene oxide to the compound (2-3):CF₂ClCFClCF(OCF₃)CF₂OCF═CF₂  (2-1)CF₂ClCFClCF(OCF₃)CF₂OCF(CF₃)COF  (2-2)CF₂ClCFClCF(OCF₃)COF  (2-3)

The compound (2-3) is preferably produced by the following method 1 or2.

Method 1:

A method wherein the following compound (A) and the following compound(B) are subjected to an esterification reaction to form the followingcompound (C), the compound (C) is fluorinated to form the followingcompound (D), and the compound (D) is subjected to decomposition of theester bond.CH₂ClCHClCH(OCH₃)CH₂OH  (A)R^(f2)COX  (B)CH₂ClCHClCH(OCH₃)CH₂OCOR^(f2)  (C)CF₂ClCFClCF(OCF₃)CF₂OCOR^(f2)  (D)

In the above formulae, R^(f2) is a perfluoro monovalent saturatedorganic group, and X is a halogen atom.

Method 2:

A method wherein the following compound (A¹) is reacted with thefollowing compound (B) for esterification to form the following compound(C¹), the compound (C¹) is chlorinated to form the following compound(C), the compound (C) is fluorinated to form the following compound (D),and the compound (D) is subjected to decomposition of the ester bond.CH₂═CHCH(OCH₃)CH₂OH  (A¹)R^(f2)COX  (B)CH₂═CHCH(OCH₃)CH₂OCOR^(f2)  (C¹)CH₂ClCHClCH(OCH₃)CH₂OCOR^(f2)  (C)CF₂ClCFClCF(OCF₃)CF₂OCOR^(f2)  (D)

In the above formulae, X is a halogen atom, and R^(f2) is a perfluoromonovalent saturated organic group.

R^(f2) is preferably a perfluoroalkyl group, a perfluoro(etheric oxygenatom-containing alkyl) group, a perfluoro(partially chloroalkyl) group,or a perfluoro(partially chloro(etheric oxygen atom-containing alkyl))group, particularly preferably a perfluoro(partially chloro(ethericoxygen atom-containing alkyl)) group, especially preferablyCF₂ClCFClCF(OCF₃)CF₂—.

As specific examples of R^(f2), the following groups may be mentioned,wherein n is an integer of from 1 to 9, r is an integer of from 0 to 10,each of m and p is an integer of at least 0, preferably an integer offrom 0 to 10, and k is an integer of at least 1, preferably an integerof from 1 to 10.

CF₃—,

CF₃(CF₂)_(n)—,

CF₃(CF₂)_(m)O(CF₂)_(k)—,

CF₃(CF₂)_(m)OCF(CF₃)—

CF₂ClCFCl(CF₂)_(p)—

CF₂ClCFClCF(OCF₃)CF₂—,

CF₂ClCFClCF(O(CF₂)_(r)CF₃)CF₂—

Further, as R^(f2), CF₂ClCFClCF(OCF₃)—is preferred.

X is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom,preferably a fluorine atom, a chlorine atom or a bromine atom,particularly preferably a fluorine atom.

In the above methods 1 and 2, the esterification reaction can be carriedout under conditions for a usual esterification reaction. Such areaction may be carried out by using a solvent (hereinafter referred toas an esterification solvent), but it is preferred not to use anesterification solvent, from the viewpoint of the volume efficiency.

In the esterification reaction, HX will be formed as a by-product. WhenX is a fluorine atom, HF will be formed as a by-product, and as a HFscavenger, an alkali metal fluoride (such as NaF, KF or the like) or abase such as a trialkylamine or pyridine, may be present in the reactionsystem. In a case where such a HF scavenger is employed, its amount ispreferably from 1 to 10 times by mol, to the compound (B) or thecompound (B¹). In a case where no such a HF scavenger is used, thereaction may be carried out at a reaction temperature where HF can bevaporized, and HF is discharged out of the system as carried by anitrogen stream.

The lower limit temperature for the esterification reaction is, in ausual case, preferably at least −50° C., and the upper limit ispreferably whichever is lower +100° C. or the boiling point of theesterification solvent. Further, the reaction time may optionally bechanged depending upon the supply rate of the raw material and theamount of the compound to be used for the reaction. The reactionpressure (the gauge pressure, the same applies hereinafter) ispreferably from 0 to 2 MPa.

In the method 2, the compound (C¹) formed by the esterificationreaction, is chlorinated to form the compound (C). The chlorinationreaction can be carried out under the operational and reactionconditions for a usual chlorination reaction by means of a chlorinatingagent. The chlorinating agent is preferably chlorine (Cl₂). In a casewhere chlorine is used, the amount is preferably from 1 to 10 times bymol, particularly preferably from 1 to 5 times by mol, to the compound(C¹). The reaction of the compound (C¹) with the chlorinating agent maybe carried out by using a solvent (hereinafter referred to as achlorination solvent), but it is preferred not to use a chlorinationsolvent from the viewpoint of the volume efficiency. In a case where achlorination solvent is employed, it is preferred to employ ahalogenated hydrocarbon solvent. The halogenated hydrocarbon solventmay, for example, be dichloromethane or chloroform. The amount of thechlorination solvent is preferably from 0.5 to 5 times the mass of thecompound (C¹). Further, the temperature for the chlorination reaction ispreferably from −78° C. to +200° C.

With respect to the compound (C) in the methods 1 and 2, a fluorinationreaction is then carried out. The fluorination reaction may be carriedout by an electrochemical fluorination method (ECF method), a method forfluorination by means of cobalt fluoride, or a method for a reactionwith fluorine gas in a gas phase, but such methods have various problemssuch that the yield of the fluorinated reaction product is very small, aspecial apparatus is required, the operation is difficult, etc.Accordingly, in the present invention, it is preferred to employ aliquid phase fluorination method wherein a reaction with fluorine iscarried out in a liquid phase, from the viewpoint of a high yield,simplicity of the operation, etc. Now, the liquid phase fluorinationmethod will be described.

The fluorine content in the compound (C) is preferably appropriatelychanged depending upon the type of the liquid phase to be used for thefluorination reaction. The lower limit of the fluorine content (theproportion of the total amount of fluorine atoms to the molecular weightof the substrate to be fluorinated) is usually preferably 10 mass %,particularly preferably 30 mass %. Further, the upper limit ispreferably 86 mass %, particularly preferably 80 mass %.

Further, it is preferred to adjust the structure of R^(f2) so that themolecular weight of the compound (C) will be from 300 to 1000. It ispreferred that the molecular weight is within the above range, since thefluorination reaction in the liquid phase can be carried out smoothly.If the molecular weight is too small, the substrate to be fluorinated,tends to be easily vaporized, whereby a decomposition reaction in a gasphase is likely to take place during the fluorination reaction in theliquid phase. On the other hand, if the molecular weight is too large,purification of the substrate to be fluorinated tends to be difficult.

The following compounds may be mentioned as examples of the compound (C)and the compound (C¹) as substrates to be fluorinated. Here, m in thefollowing formulae is as defined above.CH₂ClCHClCH(OCH₃)CH₂OCOCF(CF₃)O(CF₂)_(m)CF₃,CH₂ClCHClCH(OCH₃)CH₂OCOCF₂CF(OCF₃)CFClCF₂Cl,CH₂═CHCH(OCH₃)CH₂OCOCF(CF₃)O(CF₂)_(m)CF₃,CH₂═CHCH(OCH₃)CH₂OCOCF₂CF(OCF₃)CFClCF₂Cl.

The liquid phase fluorination is preferably carried out by introducingfluorine in the solvent constituting the liquid phase and reacting itwith the compound. As the fluorine, 100% fluorine gas may be employed,or fluorine gas diluted with an inert gas may be employed. As such aninert gas, nitrogen gas or helium gas is preferred, and nitrogen gas isparticularly preferred. The fluorine gas content in the gas mixture ofthe inert gas and the fluorine gas, is preferably at least 5 vol % fromthe viewpoint of the efficiency, particularly preferably from 5 to 30vol % from the viewpoint of withdrawing chlorine or preventing migrationof chlorine.

As the solvent (hereinafter referred to as a fluorination solvent), asolvent which essentially contains a C—F bond without containing a C—Hbond, is preferred. Further, a perfluoroalkane or an organic solventobtained by perfluorinating a known organic solvent having in itsstructure at least one atom selected from a chlorine atom, a nitrogenatom and an oxygen atom, is preferred. Further, as the fluorinationsolvent, it is preferred to employ a solvent having a high solubility ofthe compound (C), and it is particularly preferred to employ a solventcapable of dissolving at least 1 mass %, particularly preferably atleast 5 mass %, of the compound (C), based on the total amount of thesolvent and the compound (C).

Examples of such a fluorination solvent include the compound (D) as aproduct of a fluorination reaction, the compound (B), perfluoroalkanes(trade name: FC-72, etc.), perfluoroethers (trade name: FC-75, FC-77,etc.), perfluoropolyethers (trade name: KRYTOX, FOMBLIN, GALDEN, DEMNUM,etc.), chlorofluorocarbons (trade name: FLON LUBE),chlorofluoropolyethers, perfluoroalkylamines (such asperfluorotrialkylamine, etc.), and inert fluids (trade name:FLUORINERT). Among them, the compound (D) is preferred as thefluorination solvent. When the compound (D) is used, there will be anadvantage that post treatment after the reaction may be easy. The amountof the fluorination solvent is preferably at least 5 times by mass,particularly preferably from 10 to 100 times by mass, relative to thecompound (C).

The reaction system for the liquid phase fluorination reaction ispreferably a batch system or a continuous system. From the viewpoint ofthe yield and selectivity of the reaction, the reaction system ispreferably the following system 2. Further, as the fluorine gas, onediluted with an inert gas such as nitrogen gas may be employed either ina case where the reaction is carried out by a batch system or a casewhere the reaction is carried out by a continuous system. The followingsystems may be mentioned as methods for the fluorination reaction by acontinuous system.

System 1

A method wherein into a reactor, the compound (C) and the fluorinationsolvent are charged, and stirring is initiated. Then, the reaction iscarried out while continuously supplying fluorine gas into thefluorination solvent at the prescribed reaction temperature and reactionpressure.

System 2

A method wherein into a reactor, the fluorination solvent is charged andstirred, and then the compound (C) and fluorine gas are continuously andsimultaneously supplied into the fluorination solvent in a prescribedmolar ratio at a predetermined reaction temperature and reactionpressure.

When supplying the compound (C), it may or may not be diluted with thefluorination solvent. In a case where it is diluted, the amount of thefluorination solvent to the mass of the compound (C) is preferablyadjusted to be at least 5 times, particularly preferably at least 10times.

In the liquid phase fluorination reaction, in order to let thefluorination reaction proceed efficiently, it is preferred to chargefluorine gas so that at a later stage of the reaction, the amount offluorine will be always excess in equivalent to hydrogen atoms presentin the compound (C) and it is particularly preferred to charge fluorinegas so that it will be at least 1.5 times by equivalent (i.e. at least1.5 times by mol), from the viewpoint of the selectivity. The amount offluorine is preferably maintained to be always in excess from theinitiation to the end of the reaction.

The reaction temperature for the liquid phase fluorination reaction ispreferably at least −60° C. and at most the boiling point of thecompound (C). It is particularly preferably from −50° C. to +100° C.from the viewpoint of the yield by the reaction, the selectivity and theindustrial operation efficiency, and it is especially preferably from−20° C. to +50° C. from the viewpoint of withdrawing chlorine orpreventing migration of chlorine. The reaction pressure for thefluorination reaction is not particularly limited, and it isparticularly preferably from atmospheric pressure to 2 MPa (gaugepressure, and the pressure will hereinafter be represented by a gaugepressure unless otherwise specified) from the viewpoint of the yield bythe reaction, the selectivity and the industrial operation efficiency.

Further, in the liquid phase fluorination, it is preferred to let a C—Hbond-containing compound be present in the reaction system, or to carryout radiation with ultraviolet rays. For example, it is preferred to addthe C—H bond-containing compound to the action system or to carry outirradiation with ultraviolet rays at a later stage of the fluorinationreaction, whereby hydrogen atoms present in the compound C), which arehardly fluorinated, can efficiently be fluorinated, and the conversioncan remarkably be improved. The time for irradiation with ultravioletrays s preferably from 0.1 to 3 hours.

The C—H bond-containing compound is preferably an organic compound otherthan the compound (C), particularly preferably an aromatic hydrocarbon,especially preferably benzene, toluene or the like. The amount of theC—H bond-containing compound is preferably from 0.1 to 10 mol %,particularly preferably from 0.1 to 5 mol %, based on the hydrogen atomsin the compound (C).

The C—H bond-containing compound is preferably added in a state wherefluorine is present in the reaction system. Further, in a case where theC—H bond-containing compound is added, the reaction system is preferablypressurized. The pressurizing pressure is preferably from 0.01 to 5 MPa.

The liquid phase fluorination reaction is carried out until hydrogenatoms in the compound (C) are perfluorinated. In the liquid phasefluorination reaction, hydrogen atoms are replaced by fluorine atoms,and in a case where an unsaturated bond is present, fluorine atoms willbe added to the unsaturated bond portion.

In the liquid phase fluorination reaction, HF will be formed as aby-product. In order to remove HF formed as a by-product, it ispreferred to let a HF scavenger be coexistent in the reaction system orto contact a HF scavenger and the discharge gas at the gas outlet of thereactor. As such a HF scavenger, a base such as an alkali metal fluoride(such as NaF, KF or the like) is lo preferred, and such a base may bepresent in the reaction system. As the HF scavenger, NaF is particularlypreferred.

In a case where the HF scavenger is incorporated in the reaction system,its amount is preferably from 1 to 20 times by mol, more preferably from1 to 5 times by mol, to the total amount of hydrogen atoms present inthe compound (C). In a case where the HF scavenger is disposed at thegas outlet of the reactor, it is preferred to install (a) a cooler(maintained to be preferably from 10° C. to room temperature,particularly preferably at about 20° C.), (b) a packed layer of the HFscavenger such as NaF pellets, and (c) a cooler (maintained to bepreferably from −78° C. to +10° C., more preferably from −30° C. to 0°C.) in series in the order of (a)-(b)-(c). Further, a liquid-returningline may be installed to return a condensed liquid from the cooler (c)to the reactor.

Then, the compound (D) is subjected to a decomposition reaction of theester bond to obtain the desired compound (2-3).

The decomposition reaction is a reaction to break —CF₂OCO— to form two—COF groups. Such a reaction is preferably carried out by a pyrolysisreaction or by a decomposition reaction carried out in the presence of anucleophilic agent or an electrophilic agent.

The pyrolysis reaction can be carried out by heating the compound (D).The reaction system for the pyrolysis reaction is preferably selecteddepending upon the boiling point and stability of the compound (D).

For example, for a pyrolysis reaction in a case where the compound (D)is a compound which is easily vaporized, it is possible to employ avapor phase pyrolysis method wherein decomposition is carried out in avapor phase continuously, and the outlet gas containing the obtainedcompound (2-3) is condensed and recovered. The reaction temperature forthe vapor phase pyrolysis method is preferably from 50 to 350° C.,particularly preferably from 50 to 300° C., especially preferably from150 to 250° C. Further, in the reaction system, an inert gas which isnot directly involved in the reaction, may be present. As such an inertgas, nitrogen gas or carbon dioxide gas may, for example, be mentioned.The inert gas is preferably incorporated in an amount of from about 0.01to 50 vol %, based on the compound (D). If the amount of the inert gasto be incorporated, is large, the recovery of the product may sometimesdecrease.

On the other hand, for a pyrolysis reaction in a case where the compound(D) is a hardly vaporizable compound, it is preferred to employ a liquidphase pyrolysis method wherein the liquid is heated in the state ofliquid in the reactor. The reaction pressure in such a case is notlimited. In a usual case, products formed by decomposition of the esterbond have lower boiling points. Accordingly, it is preferred to carryout the reaction while continuously withdrawing the low boiling pointproducts by means of a reactor equipped with a distillation column.Otherwise, a method may be employed wherein the products are withdrawnfrom the reactor all at once after completion of the heating. Thereaction temperature for such a liquid phase pyrolysis method ispreferably from 50 to 300° C., particularly preferably from 80 to 250°C.

In a case where pyrolysis is carried out by a liquid phase pyrolysismethod, it may be carried out in the absence of a solvent or in thepresence of a solvent (hereinafter referred to as a decompositionreaction solvent). However, it is preferred to carry out the reaction inthe absence of any solvent. In a case where the decomposition reactionsolvent is employed, the solvent is not particularly limited so long asit is a solvent which does not react with the compound (D) and iscompatible with the compound (D) and which does not react with thecompound (2-3). Further, as the decomposition reaction solvent, it ispreferred to select one which can easily be separated at the time ofpurification of the product.

As a specific example of the decomposition reaction solvent, an inertsolvent such as a perfluorotrialkylamine or perfluoronaphthalene, or achlorotrifluoroethylene oligomer (such as FLON LUBE, trade name,manufactured by Asahi Glass Company, Limited) having a high boilingpoint among chlorofluorocarbons, is preferred. Further, thedecomposition reaction solvent is preferably used in an amount of from10 to 1000 mass %, based on the compound (D).

Further, the compound (D) may be subjected to decomposition of the esterbond by reacting it with a nucleophilic agent or an electrophilic agentin a liquid phase. In such a case, the reaction may be carried out inthe absence of any solvent or in the presence of a decompositionreaction solvent. The nucleophilic agent is preferably a fluorine ion(F⁻), particularly preferably a fluorine ion derived from an alkalimetal fluoride. As such an alkali metal fluoride, NaF, NaHF₂, KF or CsFis preferred, and particularly preferred is NaF. By carrying out thepyrolysis reaction in the presence of NaF, it is possible to carry outthe pyrolysis reaction at a low temperature, whereby it is possible toprevent a decomposition reaction of the compound.

The nucleophilic agent to be used at the initial stage of the reaction,is preferably in a catalytic amount, but may be used in excess. Theamount of the nucleophilic agent is preferably from 1 to 500 mol %,particularly preferably from 10 to 100 mol %, especially preferably from5 to 50 mol %, based on the compound (D). The lower limit of thereaction temperature is preferably at least −30° C., and the upper limitis whichever is lower the boiling point of the solvent or the boilingpoint of the compound (D), and usually, it is particularly preferablyfrom −20° C. to +250° C. The decomposition reaction is preferablycarried out by means of a reactor equipped with a distillation column.

In the decomposition reaction of the ester bond, together with thecompound (2-3), the compound (B) represented by the formula R^(f2)COX,will be formed.

The compound (B) wherein R^(f2) is CF₂ClCFClCF(OCF₃)CF₂—, is the same asthe compound of the formula (2-3), whereby no separation operation ofthe formed product is required. However, in a case where R^(f2) is agroup other than CF₂ClCFClCF(OCF₃)CF₂—, it is preferred to separate thecompound (B) in the product. And, such a compound (B) is preferablyreused as a compound (B) to be reacted with the compound (A) or thecompound (A¹).

The reaction for adding hexafluoropropylene oxide to the compound (2-3)to obtain the compound (2-2), is preferably carried out by reacting ametal fluoride to the compound (2-3) in a solvent and reacting it withhexafluoropropylene oxide. The reaction temperature for the reaction ispreferably at most 50° C., particularly preferably from 5 to 25° C. Themetal fluoride may, for example, be potassium fluoride, cesium fluoride,sodium fluoride or silver fluoride. The solvent for the reaction ispreferably an ether solvent or an aprotic polar solvent. The reactionpressure of hexafluoropropylene oxide is preferably from 0 to 1 MPa,particularly preferably from 0.1 to 0.5 MPa.

Further, the compound (2-2) can be synthesized from the compound (2-4)by the method disclosed in WO01/46093. Namely, the compound (2-4) isreacted with the compound (2-5) to obtain a compound (2-6). Further, thecompound (2-6) is contacted with chlorine gas to obtain a compound(2-7). The compound (2-7) is subjected to liquid phase fluorination toobtain the compound (2-2).CF₂ClCFClCF(OCF₃)CF₂OCF(CF3)COF  (2-2)CH₂═CHCH(OCH₃)CH₂OCH(CH₃)CH₂OH  (2-4)R^(f3)COF  (2-5)CH₂═CHCH(OCH₃)CH₂OCH(CH₃)CH₂OCOR^(f3)  (2-6)CH₂ClCHClCH(OCH₃)CH₂OCH(CH₃)CH₂OCOR^(f3)  (2-7)

In the above formulae, R^(f3) is preferably a fluoroalkyl group, afluoro(partially chloroalkyl) group, a fluoro(hetero atom-containingalkyl) group or a fluoro(partially chloro(hetero atom-containing alkyl))group, particularly preferably such a group which is perfluorinated.

The compound (2-2) will then be pyrolyzed to obtain the compound (2-1).The pyrolysis can be carried out by a method of directly pyrolyzing thecompound (2-2), or a method of converting the compound (2-2) to analkali salt of the corresponding carboxylic acid, followed by pyrolysis.Further, it is also possible to employ a method wherein the active group(—COF) in the compound (2-2) is converted to a practically stable group,which is then converted to an alkali salt of the carboxylic acid,followed by pyrolysis. As such a method, a method may, for example, bementioned wherein the compound (2-2) is reacted with an alkanol toconvert it to an alkyl ester of the corresponding carboxylic acid, whichis then converted to an alkali salt, followed by pyrolysis.

In a case where the compound (2-2) is directly pyrolyzed, it ispreferred that the compound (2-2) is vaporized, then if necessary,diluted with an inert gas such as nitrogen gas, and contacted with asolid basic salt or glass beads at a high temperature. The reactiontemperature is usually from 200 to 500° C., particularly preferably from250 to 350° C. As the solid basic salt, sodium carbonate, potassiumcarbonate or sodium phosphate may, for example, be used, and sodiumcarbonate is particularly preferred.

Whereas, in a case where the compound (2-2) is converted to an alkalimetal salt of the corresponding carboxylic acid and then pyrolyzed, itis preferred firstly to react the compound (2-2) with an alkali metalhydroxide to form an alkali metal salt of the carboxylic acid. Thepyrolysis reaction of this alkali metal salt is preferably carried outfrom 100 to 300° C., particularly preferably from 150 to 250° C. By thepyrolysis reaction, the compound (2-1) will be obtained. The pyrolysisreaction of an alkali metal salt of the carboxylic acid is preferred,since it can be carried out at a low temperature as compared with themethod of carrying out the pyrolysis directly, and the yield is alsohigh. The production of the alkali metal salt of the carboxylic acid ispreferably carried out by using water or an alcohol as a solvent, and itis preferred that the obtained alkali metal salt is sufficiently driedand then pyrolyzed. Further, as the alkali metal salt, a sodium salt ora potassium salt may be mentioned, and a potassium salt is preferred,since it can be pyrolyzed at a lower temperature.

Further, the fluorinated diene compound (1) of the present invention canbe obtained also by carrying out dehalogenation at halogen atoms otherthan fluorine atoms of the compound (3). A compound (3-1) as a preferredembodiment of the compound (3) wherein R^(f) is a trifluoromethyl group,and Z¹, Z², Z³ and Z are chlorine atoms, can be produced as follows.Namely, a compound (2-3) is esterified to produce a compound (3-2)(wherein R is an alkyl group). Otherwise, the compound (3-2) may also beobtained by ester exchange of the above-mentioned compound (D) and analkanol represented by the formula ROH (wherein R is as defined above).Further, the compound (3-2) is reduced to obtain a compound (3-3). Then,this compound is reacted with an alkali metal hydride or an alkali metalto form a metal alkoxide (3-3a) (wherein M is an alkali metal atom),which is then reacted with tetrafluoroethylene to obtain a compound(3-4). This compound (3-4) is further contacted with chlorine gas to addchlorine atoms to the unsaturated bond thereby to produce a compound(3-5). Finally, hydrogen atoms in this compound (3-5) are all replacedby fluorine atoms by liquid phase fluorination to obtain the compound(3-1).CF₂ClCFClCF(OCF₃)CF₂OCFClCF₂Cl  (3-1)CF₂ClCFClCF(OCF₃)COF  (2-3)CF₂ClCFClCF(OCF₃)CO₂R  (3-2)CF₂ClCFClCF(OCF₃)CH₂OH  (3-3)CF₂ClCFClCF(OCF₃)CH₂OM  (3-3a)CF₂ClCFClCF(OCF₃)CH₂OCF═CF₂  (3-4)CF₂ClCFClCF(OCF₃)CH₂OCFClCF₂Cl  (3-5)

The esterification of the compound (2-3) can be carried out by dropwiseadding the acid fluoride represented by the formula (2-3) into analkanol represented by the formula ROH. The temperature for the reactionis preferably from 0° C. to 20° C. R is preferably a C₁₋₄ alkyl group.On the other hand, in a case where the compound (3-2) is produced by theester exchange, usual ester exchange reaction conditions can be applied.

Then, the compound (3-2) is reduced to produce the compound (3-3). Thereduction reaction is preferably carried out, for example, by sodiumboron hydride or lithium aluminum hydride. The reaction temperature ispreferably from 0° C. to 20° C. The reduction reaction is preferablycarried out in the presence of a reaction solvent, and as the reactionsolvent, an alcohol or a non-cyclic or cyclic ether solvent may bementioned. Specifically, methanol, ethanol, isopropanol, n-butanol,t-butanol, diethyl ether, methyl t-butyl ether, tetrahydrofuran,dioxane, monoglime, diglime, triglime or tetraglime may, for example, beused. These solvents may be used alone or in combination as a mixture ofan optional ratio. By mixing the solvent, it is possible to control thereaction. In the case of a mixture, it is preferred to employ an ethersolvent in an amount of from 1 to 10 times by volume, to an alcohol. Tocontrol a side reaction, it is particularly preferred to use diethylether or tetrahydrofuran as mixed in an amount of from 1 to 2 times byvolume to ethanol.

Then, the compound (3-3) is reacted with an alkali metal hydride or analkali metal (such as sodium) to obtain the compound (3-3a). Thetemperature for such a reaction is preferably from 0° C. to 20° C. Thealkali metal atom in the alkali metal hydride may, for example, besodium, lithium, potassium or cesium. Such a reaction may be carried outin the presence of a reaction solvent, and as such a reaction solvent, anon-cyclic or cyclic ether solvent or an aprotic polar solvent may beemployed. Specifically, diethyl ether, methyl t-butyl ether,tetrahydrofuran, dioxane, monoglime, diglime, triglime, tetraglime,acetonitrile, benzonitrile, sulfolane, dimethylacetamide ordimethylsulfoxide may, for example, be used. The formed compound (3-3a)is preferably used for the next reaction together with the reactionsolvent, without isolating it.

Then, tetrafluoroethylene is added to the compound (3-3a) to obtain thecompound (3-4). This reaction is preferably carried out by transferringthe reaction product containing the compound (3-3a) as it contains thereaction solvent, to an autoclave and introducing tetrafluoroethylene.The reaction temperature for the reaction is preferably from −10 to +50°C., particularly preferably from 0 to +30° C. The reaction pressure ispreferably from 0.5 to 3.5 MPa, particularly preferably from 1.0 to 2.2MPa. Further, it is preferred to raise the reaction temperature aftercompletion of the introduction of tetrafluoroethylene, and thetemperature raised is preferably from 30 to 100° C., particularlypreferably from 50 to 70° C. The reaction time is preferably from 30minutes to 120 hours, particularly preferably from 5 hours to 10 hours.

Then, the compound (3-4) is chlorinated to obtain the compound (3-5)having chlorine atoms introduced to the unsaturated double bond of thevinyl ether. This reaction involves heat generation, and it isaccordingly preferred to carry out the reaction while cooling thesystem. The reaction temperature for this reaction is preferablyadjusted from −50 to 100° C., particularly preferably from −20 to 10° C.

Then, the compound (3-5) is reacted with fluorine in a liquid phase toobtain the compound (3-1). This can be carried out in the same manner asthe above-mentioned fluorination. And, the compound (3-1) is subjectedto the above-mentioned dehalogenation reaction, whereby the compound (1)of the present invention can be produced.

The fluorinated diene compound (1) of the present invention ispolymerizable, and is useful as a monomer for the production of afluoropolymer. This fluorinated diene compound (1) undergoes cyclicpolymerization alone by an action of a radical polymerization initiatorto form a polymer having monomer units having fluorinated aliphaticcyclic structures in its main chain. Further, the fluorinated dienecompound (1) may be copolymerized with another monomer.

Namely, the present invention presents a fluoropolymer comprisingmonomer units formed by cyclopolymerization of the fluorinated dienecompound (1), or a fluoropolymer comprising monomer units formed bycyclopolymerization of the fluorinated diene compound (1) and monomerunits formed by polymerization of another monomer polymerizable with thefluorinated diene compound (1). The proportion of the monomer units ofthe fluorinated diene compound (1) contained in the fluoropolymer ispreferably from 30 to 100 mol %, particularly preferably from 50 to 100mol %, based on the total monomer units. Further, the molecular weightof the fluoropolymer is preferably from 500 to 1×10⁶, particularlypreferably from 500 to 5×10⁵.

The monomer units formed by cyclopolymerization of the fluorinated dienecompound (1) are preferably either one of monomer units represented bythe following formulae. The monomer units present in the fluoropolymermay be of one type, or of two or more types.

Another polymerizable monomer is not particularly limited so long as itis a radically polymerizable monomer, and it may, for example, be afluorinated monomer other than the compound (1), a hydrocarbon monomeror other monomer. For example, it may be an olefin such as ethylene, afluoroolefin such as tetrafluoroethylene, a fluorinated vinyl ethermonomer such as a perfluoro(alkyl vinyl ether), a cyclopolymerizablefluorinated diene (other than the fluorinated diene compound (1)) suchas a perfluoro(allyl vinyl ether) or a monomer having a fluorinatedaliphatic ring structure, such as perfluoro(2,2-dimethyl-1,3-dioxole).As another polymerizable monomer, at least one member selected fromtetrafluoroethylene, perfluoro(butenyl vinyl ether) andperfluoro(2,2-dimethyl-1,3-dioxole) is particularly preferred. Theproportion of monomer units of another polymerizable monomer ispreferably from 0 to 70 mol %, particularly preferably from 0 to 50%,based on the total monomer units in the fluoropolymer. Such anothermonomer may be used alone or in combination of two or more types.

As the radical polymerization initiator to be used for polymerization ofthe fluorinated diene compound (1), a polymerization initiator commonlyused for radical polymerization of e.g. an azo compound, an organicperoxide or an inorganic peroxide, may be used. Specifically,diisopropyl peroxydicarbonate, an azo compound such as2,2′-azobis(2-amidinopropane) dihydrochloride,4,4′-azobis(4-cyanopentanoic acid),2,2′-azobis(4-methoxy-2,3-dimethylvaleronitrile) or1,1′-azobis(1-cyclohexanecarbonitrile), an organic peroxide such asbenzoyl peroxide, perfluorobenzoyl peroxide, perfluorononanoyl peroxideor methyl ethyl ketone peroxide, or an inorganic peroxide such as K₂S₂O₈or (NH₄)₂S₂O₈, may, for example, be mentioned.

The polymerization method is not particularly limited, and it may, forexample, be a polymerization wherein the fluorinated diene compound (1)is directly polymerized (so-called bulk polymerization), a solutionpolymerization wherein the fluorinated diene compound (1) is dissolvedin a fluorinated hydrocarbon, a chlorinated hydrocarbon, a chlorinatedfluorohydrocarbon, an alcohol, a hydrocarbon or other organic solventsand polymerized, a suspension polymerization wherein polymerization iscarried out in an aqueous medium, if necessary, in the presence of anorganic solvent, or an emulsion polymerization wherein polymerization iscarried out in an aqueous medium in the presence of an emulsifier. Thetemperature and the pressure for the polymerization are not particularlylimited, and it is advisable to suitably set them taking intoconsideration the boiling point of the fluorinated diene compound, theheating source, removal of the polymerization heat, etc. Thepolymerization temperature is usually preferably from 0 to 200° C.,particularly preferably from 30 to 100° C. The polymerization pressuremay be a reduced pressure or an elevated pressure, and it is practicallypreferably from atmospheric pressure to about 10 MPa, more preferablyfrom atmospheric pressure to about 5 MPa.

The fluoropolymer of the present invention has characteristics such thatit is excellent in transparency, the glass transition temperature ishigh, and the heat resistance is high. By utilizing suchcharacteristics, the fluoropolymer of the present invention is useful byitself as an optical resin material excellent in heat resistance, to beused for an optical fiber, an optical waveguide or an opticaltransmitter such as a lens. Further, the fluoropolymer of the presentinvention has characteristics that it is optically transparent, and ithas a low refractive index as compared with a conventional transparentfluorocarbon resin (such as CYTOP, trade name, manufactured by AsahiGlass Company, Limited or Teflon AF, trade name, manufactured byDuPont). By utilizing such characteristics, the fluoropolymer of thepresent invention may be combined with a conventional transparentfluorocarbon resin having a low refractive index and use as a highperformance optical device excellent in optical transparency, such as anoptical fiber or an optical waveguide.

Particularly, a plastic optical fiber comprising a core made of amixture comprising the fluoropolymer of the present invention and arefractive index-increasing agent, and a clad made of the fluoropolymerof the present invention, has excellent heat resistance. Such a plasticoptical fiber may be used as of a step index type or a refractiveindex-distribution type, and it is particularly preferably a plasticoptical fiber of refractive index-distribution type. As the aboverefractive index-increasing agent, a fluorinated low molecular weightcompound is preferred, since the transparency of the obtainable mixturewill be excellent. As such a fluorinated low molecular weight compound,perfluoro(triphenyltriazine), perfluoro(1,3,5-triphenylbenzene) orchlorotrifluoroethylene oligomer may, for example, be preferablymentioned. Such low molecular weight compounds may be used alone or incombination as a mixture of two or more of them.

The following methods may be mentioned as the method for producing aplastic optical fiber of refractive index-distribution type.

For example, a method wherein a columnar molded product of thefluoropolymer of the present invention is prepared so that at the centeraxis portion, a refractive index-increasing agent is present at apredetermined concentration, and the refractive index-increasing agentis diffused in a radial direction from the center axis portion bythermal diffusion to form a refractive index distribution, whereupon theobtained columnar molded product is used as a preform to form an opticalfiber (JP-A-8-5848).

A method wherein a cylindrical molded product is prepared by thefluoropolymer of the present invention, a predetermined amount of arefractive index-increasing agent is introduced into the center portion,followed by thermal diffusion to form a cylindrical preform having arefractive index distribution, which is formed into an optical fiber(JP-A-8-334633).

Further, the fluoropolymer of the present invention is soluble in afluorocarbon solvent such as perfluoro(2-butyltetrahydrofuran),perfluorooctane, perfluorohexane, perfluoro(tributylamine),perfluoro(tripropylamine), perfluorobenzene ordichloropentafluoropropane. A solution having the fluoropolymer of thepresent invention dissolved in such a solvent, is a fluoropolymersolution useful for various applications. As an application of such asolution, an application may, for example, be mentioned wherein it iscoated on a substrate such as a glass or silicon wafer by a spin coatingmethod or a spraying method, and then the solvent is vaporized fordrying to form a thin film. The amount of the fluoropolymer contained insuch a fluoropolymer solution is preferably from 0.01 to 20 mass %,particularly preferably from 0.1 to 10 mass %.

Further, the fluoropolymer of the present invention may be subjected toheat treatment or fluorine gas treatment, whereby the terminal groupscan easily be substituted. And, by changing the structure of terminalgroups by the treating method, the adhesion property to varioussubstrates can be changed. For example, carboxyl groups can beintroduced to the terminals by heating the fluoropolymer of the presentinvention at a temperature of at least 200° C. in the presence of air,followed by treatment with water. Otherwise, it is possible to removereactive functional groups at the terminals by reacting them withfluorine gas, whereby it is possible to improve the thermal stability ofthe fluoropolymer.

EXAMPLES

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted by such Examples. In the following,gas chromatography will be referred to as GC, a nuclear magneticresonance spectrum analysis as NMR, a gas chromatography mass spectrumas GC-MS, tetramethylsilane as TMS, 1,1,2-trichlorotrifluoroethane asR-113, and dichloropentafluoropropane as R-225. Further, the GC purityis meant for the purity obtained from the peak area ratio by gaschromatography. Further, the refractive index was measured by means ofAbbe's refractometer, and the glass transition temperature (T_(g)) wasmeasured by means of a differential scanning calorimetry (DSC).

Example 1 Preparation of CH₂═CHCH(OCH₃)CH₂OCOCF(CF₃)OCF₂CF₂CF₃

CH₂═CHCH(OCH₃)CH₂OH (270 g) was charged together with NaF (334 g) into a2 L pressure resistant reactor equipped with a reflux condenser having acooling medium of 20° C. circulated, and stirred at −10° C.

While bubbling nitrogen gas in the reactor to discharge HF formed as aby-product by the reaction, out of the system from the upper refluxcondenser, FCOCF(CF₃)OCF₂CF₂CF₃ (1055 g) was dropwise added over aperiod of 1.5 hours. At that time, the temperature was adjusted so thatthe internal temperature of the reactor became at most 0° C. Aftercompletion of the dropwise addition, stirring was carried out at 30° C.for 18 hours to complete the reaction. After completion of the reaction,NaF contained in the crude solution was filtered off to obtain a crudeproduct (981 g) (yield: 86.4%). As a result of the analysis by NMR,formation of the above identified compound was confirmed.

¹H-NMR (300.4 MHz, solvent: CDCl₃, standard: TMS) δ (ppm): 3.29 (s, 3H),3.85 to 3.90 (m, 1H), 4.24 to 4.45 (m, 2H), 5.34 (s, 1H), 5.39 (d, J=8.4Hz, 1H), 5.59 to 5.71 (m, 1H).

¹⁹F-NMR (282.7 MHz, solvent: CDCl₁₃, standard: CFCl₃) δ (ppm): −81.8(3F), −82.6 (3F), −79.9 to −87.5 (2F), −130.2 (2F), −132.3 (1F).

Example 2 Preparation of CH₂ClCHClCH(OCH₃)CH₂OCOCF(CF₃)OCF₂CF₂CF₃

CH₂═CHCH(OCH₃)CH₂OCOCF(CF₃)OCF₂CF₂CF₃ (981 g) obtained in Example 1, wascharged into a 2 L three-necked flask cooled to 0° C. and equipped witha Dimroth condenser, and with stirring at from −10 to 0° C., chlorinegas was introduced at a rate of 0.8 g/min to carry out the reaction.When 170 g of chlorine gas was introduced, the reaction was terminatedto obtain a crude liquid (1084 g).

The obtained crude liquid was purified by distillation under a reducedpressure of from 0.8 to 0.9 kPa (absolute pressure) to obtain a product(744 g). As a result of the analyses by NMR and GC, it was confirmedthat the above identified compound was formed as a mixture of threetypes of diastereomers having a GC purity of 98%.

¹H-NMR (300.4 MHz, solvent: CDCl₃, standard: TMS) δ (ppm): 3.45 (d,J=1.5 Hz) and 3.47 (s) and 3.55 (d J=0.6 Hz) total 3H, 3.56 to 3.80 (m,2H), 3.82 to 4.12 (m, 2H), 4.43 to 4.57 (m, 1H), 4.65 (dd, J=6.3 Hz,11.4 Hz) and 4.89 (ddd, J=42.4 Hz, 12.0 Hz, 3.0 Hz) and 5.49 (q, J=5.1Hz) total 1H.

¹⁹F-NMR (376.0 MHz, solvent: CDCl₃, standard: CFCl₃) δ (ppm): −79.93 to−80.65 (1F), −81.72 to −81.80 (3F), −82.47 to −82.56 (3F), −86.46 to−87.22 (1F), −130.07 to −130.19 (2F), −132.26 to −132.47 (1F).

Example 3 Preparation of CF₂ClCFClCF(OCF₃)CF₂OCOCF(CF₃)OCF₂CF₂CF₃ By aFluorination Reaction

Into a 3 L autoclave made of nickel, CF₃CF₂CF₂OCF(CF₃)CF₂OCF(CF₃)COF(3523 g, hereinafter referred to as the solvent A) was charged, stirredand maintained at 5° C. At the gas outlet of the autoclave, a condensermaintained at −10° C. was installed. Nitrogen gas was blown thereintofor 3.5 hours, and then fluorine gas diluted with nitrogen gas to 20%(hereinafter referred to as the diluted fluorine gas) was blownthereinto at a flow rate of 26.52 L/hr for one hour. Then, whilesupplying fluorine gas at the same flow rate, a part (415 g) ofCH₂ClCHClCH(OCH₃)CH₂OCOCF(CF₃)OCF₂CF₂CF₃ obtained in Example 2 wasinjected over a period of 22.5 hours. The reaction crude liquid (261 g)was withdrawn.

Then, while supplying the diluted fluorine gas at the same flow rate,CH₂ClCHClCH(OCH₃)CH₂OCOCF(CF₃)OCF₂CF₂CF₃ (642 g) was injected over aperiod of 22.0 hours. A reaction crude liquid (533 g) was withdrawn.

Further, while supplying the diluted fluorine gas at the same flow rate,CH₂ClCHClCH(OCH₃)CH₂OCOCF(CF₃)OCF₂CF₂CF₃ (471 g) was injected over aperiod of 22.8 hours. The reaction crude liquid (270 g) was withdrawn.

Then, while supplying the diluted fluorine gas at the same flow rate,the reaction temperature was adjusted at 25° C. for 22 hours. Then,nitrogen gas was blown thereinto for 3.0 hours. The reaction crudeliquid (3530 g) was recovered. As a result of the analysis of thereaction crude liquid by GC-MS, it was found that the solvent A and theabove identified compound were obtained as the main components. Thereaction yield of the above identified compound was 71%.

Example 4 Preparation of CF₂ClCFClCF(OCF₃)COF (2-3) by a DecompositionReaction of an Ester Bond

Into a 300 mL four-necked flask equipped with a stirrer and a refluxcondenser, CF₂ClCFClCF(OCF₃)CF₂OCOCF(CF₃)OCF₂CF₂CF₃ (200 g, 0.31 mol)obtained in Example 3 was charged together with KF powder (9.0 g, 0.155mol), and while stirring sufficiently, the mixture was heated in an oilbath at a temperature of from 90 to 95° C. for from 0.5 to 1 hour. Afterconfirming refluxing formed as the reaction proceeded, the reactionsystem was brought to reduced pressure, and the formed product wasrecovered by distilling it and withdrawing it from the reaction systemover a period of 5 hours. Further, the crude product was distilled toobtain the above identified compound (74 g) having a GC purity of 99.9%(yield: 79%). From the NMR spectrum, it was confirmed that the aboveidentified compound is the main component.

¹⁹F-NMR (282.7 MHz, solvent: CDCl₃, standard: CFCl₃) δ (ppm): 28.4, 28.0(1F), −55.1, −55.4 (3F), −61.6 to −63.9 (2F), −121.9, −123.9 (1F),−128.7, −129.0 (1F).

Boiling point: 62° C./33.3 kPa (absolute pressure).

Example 5 Preparation of CF₂ClCFClCF(OCF₃)CF₂OCF(CF₃)COF (2-2)

Into an autoclave made of a hastelloy alloy and having an internalcapacity of 100 mL, KF (0.4 g, 7.14 mmol) was put, and after reducingthe pressure, CF₂ClCFClCF(OCF₃)COF obtained in Example 4 (37 g, 0.12mol) and tetraglime (10 g) were charged and cooled with sufficientstirring, followed by stirring for from 30 minutes to one hour whileadjusting the internal temperature to from −5° C. to +50° C. Then, theautoclave was connected to a steel bottle of hexafluoropropylene oxide,and hexafluoropropylene oxide (33 g) was added while maintaining theinternal temperature at at most 25° C. and the internal pressure atabout 0.2 MPa, followed by stirring until no decrease of the internalpressure was observed. Thereafter, hexafluoropropylene oxide was purged,followed by stirring at 25° C. for from 1 to 2 hours. Then, theautoclave was opened, and the remaining solid was removed by filtration,followed by phase separation to obtain a crude product. The crudeproduct was further distilled to obtain 5.9 g (yield: 10%) of pureCF₂ClCFClCF(OCF₃)CF₂OCF(CF₃)COF.

¹⁹F-NMR (282.7 MHz, solvent: CDCl₃, standard: CFCl₃) δ (ppm); 28.0,27.8, 27.4 (1F), −52.2 to −53.0 (3F), −63.0 to −66.5 (2F), −79.5 to−81.5 (2F), −81.2, −81.4 (3F), −128.1, −128.7 (1F), −129.2, −130.1 (1F),−131.4, −132.1 (1F).

Example 6-1 Preparation of CF₂ClCFClCF(OCF₃)CO₂CH₃ (3-2)

Into a 1 L four-necked flask made of glass and equipped with a stirrer,a reflux condenser and a dropping funnel, methanol (120 g, 3.75 mol) wasput and cooled until the internal temperature became from 5 to 10° C.,and while sufficiently stirring,CF₂ClCFClCF(OCF₃)CF₂OCOCF(CF₃)OCF₂CF₂CF₃ (380 g, 0.59 mol) obtained inExample 3 was dropwise added while maintaining the internal temperatureat from 5 to 20° C. Thereafter, while bubbling nitrogen gas in thereactor to discharge HF formed as a by-product by the reaction out ofthe system by an upper reflux condenser, stirring was continued for awhile at room temperature. Then, deionized water (340 g) was added,followed by stirring sufficiently and then by phase separation into twophases, whereupon the product of the lower layer was withdrawn. Further,the crude product was distilled to obtain 128 g of pureCF₂ClCFClCF(OCF₃)CO₂CH₃ (yield: 67%)

Example 6-2 Preparation of CF₂ClCFClCF(OCF₃)CO₂CH₃ (3-2)

Using CF₂ClCFClCF(OCF₃)COF obtained in Example 4 (40 g, 0.12 mol) andmethanol (10 g, 0.31 mol), in the same manner as in Example 6-1,CF₂ClCFClCF(OCF₃)CO₂CH₃ was obtained (36 g, yield: 94%).

¹⁹F-NMR (282.7 MHz, solvent: CDCl₃, standard: CFCl₃) δ (ppm); −55.1,−55.5 (3F), −61.8 to −64.4 (2F), −123, −126 (1F), −129.3, −129.7 (1F).

¹H-NMR (300.4 MHz, solvent: CDCl₃, standard: TMS) δ (ppm); 3.96 (CH₃).

Boiling point: 55° C./2.7 kPa.

Example 7 Preparation of CF₂ClCFClCF(OCF₃)CH₂OH (3-3) BY a ReductionReaction

Into a 2 L four-necked flask made of glass and quipped with a stirrerand a dropping funnel, sodium boron hydride (17 g, 0.46 mol), diethylether (230 g) and ethanol (200 g) were put, followed by cooling untilthe internal temperature became from 5 to 10° C. While maintaining theinternal temperature at from 5 to 20° C. with sufficient stirring,CF₂ClCFClCF(OCF₃)CO₂CH₃ (150 g, 0.46 mol) obtained in Example 6 wasdropwise added. Thereafter, while maintaining the internal temperatureat from 5 to 20° C., the reaction solution was stirred for from 2 to 3hours. Then, 1 moL/L of hydrochloric acid (310 g) was added, followed bystirring sufficiently, and extraction was carried out with diethylether. The organic layer was separated and dried over magnesium sulfate,whereupon diethyl ether was distilled off under reduced pressure. Theobtained crude product was purified by distillation to obtain 128 g(yield: 70%) of highly pure CF₂ClCFClCF(OCF₃)CH₂OH.

¹⁹F-NMR (282.7 MHz, solvent: CDCl₃, standard: CFCl₃) δ (ppm); −53.3,−53.8 (3F), −60.8 to −63.6 (2F), −125.4, −126.7 (1F), −128.9, −129.3(1F).

¹H-NMR (300.4 MHz, solvent: CDCl₃, standard: TMS) δ (ppm); 2.1 (OH), 4.0to 4.3 (CH₂).

Boiling point: 41° C./0.7 kPa (absolute pressure).

Example 8 Preparation of CF₂ClCFClCF(OCF₃)CH₂OCF═CF₂ (3-4)

Into a 2 L four-necked flask equipped with a stirrer and a droppingfunnel, sodium hydride (5.4 g, 0.13 mol) was charged, and in an inertgas atmosphere, diethyl ether (140 mL) was charged. Then, whileadjusting the internal temperature from 0 to 5° C.,CF₂ClCFClCF(OCF₃)CH₂OH (35 g, 0.12 mol) obtained in Example 7 was slowlydropwise added. Thereafter, the internal temperature was slowly raisedto room temperature, and the reaction was carried out:for 5 hours.Thereafter, the reaction solution was transferred to a 2 L autoclavewhich was preliminarily vacuumed, and introducing nitrogen to 0.5 MPa,followed by purging, was repeated three times. Then, while maintainingthe remaining nitrogen pressure at 0.05 MPa, tetrafluoroethylene (47 g,0.47 mol) was slowly introduced little by little. After the charging,the reaction temperature was raised to 70° C. to raise the internalpressure to 2.2 MPa, and the reaction was carried out for from 5 to 10hours until no more pressure decrease was observed. Then, the reactionsystem was cooled, and remaining tetrafluoroethylene was purged,whereupon the autoclave was opened.

As post-treatment of the reaction solution, methanol (9.0 g) and 1 moL/Lof hydrochloric acid (140 g) were added, followed by sufficientstirring, whereupon extraction with diethyl ether was carried out, andthe organic layer was separated and then, dried over magnesium sulfate,and diethyl ether was distilled off under reduced pressure.

The crude product thus obtained was purified by distillation to obtainpure CF₂ClCFClCF(OCF₃)CH₂OCF═CF₂ (18 g, yield: 40%).

¹⁹F-NMR (282.7 MHz, solvent: CDCl₃, standard: CFCl₃) δ (ppm); −53.3,−53.5 (F^(e), 3F), −60.8 to −63.6 (F^(i), 2F), −120.2 (F^(a), 1F,J_(ab)=99 Hz), −124.7, −126.0 (F^(g), 1F), −126.0 (F^(b), 1F, J_(bc)=108Hz), −128.9, −129.1 (F^(d), 1F), −137.4 (F^(c), 1F, J_(ac)=58 Hz).

Here, a to i in F^(a) to F^(i), correspond to the positions of fluorineatoms, as shown in the following formula:

¹H-NMR (300.4 MHz, solvent: CDCl₃, standard: TMS) δ (ppm); 4.4 to 4.7(CH₂).

Boiling point: 41° C./1.3 kPa (absolute pressure).

Example 9 Preparation of CF₂ClCFClCF(OCF₃)CH₂OCFClCF₂Cl (3-5)

Into a 100 mL three-necked flask equipped with a stirrer and a dry icecondenser, CF₂ClCFClCF(OCF₃)CH₂OCF═CF₂ (35 g, 92 mmol) obtained inExample 8 was charged and cooled until the internal temperature becamewithin a range of from −25 to −20° C., and while maintaining theinternal temperature at −10° C. to +10° C. with sufficient stirring,chlorine gas was blown thereinto. When chlorine (7.4 g, 104 mmol) gaswas introduced, the introduction was stopped, and the crude product wasrecovered. The crude product was further distilled to obtain pureCF₂ClCFClCF(OCF₃)CH₂OCFClCF₂Cl (38 g, yield: 95%).

¹⁹F-NMR (282.7 MHz, solvent: CDCl₃, standard: CFCl₃) δ (ppm); −53.3,−53.5 (3F), −60.8 to −63.6 (2F), −69.2 (2F), −74.2, −74.5 (1F), −123.3to −124.9 (1F), −128.9, −129.0 (1F).

¹H-NMR (300.4 MHz, solvent: CDCl₃, standard: TMS) δ (ppm); 4.4 to 4.7(CH₂)

Boiling point: 50° C./0.7 kPa (absolute pressure).

Example 10 Preparation of CF₂ClCFClCF(OCF₃)CF₂OCFClCF₂Cl (3-1)

Into a 500 mL autoclave made of nickel, R-113 (312 g) was charged,stirred and maintained at 25° C. At the gas outlet of the autoclave, acondenser maintained at 20° C., a NaF pellet-packed layer and acondenser maintained at −10° C. were installed in series. Further, aliquid-returning line was installed to return the liquid condensed fromthe condenser maintained at −10° C., to the autoclave. Nitrogen gas wassupplied for 1.0 hour, and then, diluted fluorine gas was supplied at aflow rate of 11.88 L/hr for one hour. Then, while supplying fluorine gasat the same flow rate, a solution having CF₂ClCFClCF(OCF₃)CH₂OCFClCF₂Cl(34 g, 75 mmol) obtained in Example 9, dissolved in R-113 (195.3 g), wasinjected over a period of 5.8 hours.

Then, while supplying fluorine gas at the same flow rate and maintainingthe reactor pressure at 0.15 MPa, a R-113 solution having a benzeneconcentration of 0.01 g/ml was injected in an amount of 9 ml whileraising the temperature from 25° C. to 40° C., whereupon the benzeneinlet of the autoclave was closed, and stirring was continued for 0.3hour. Then, while maintaining the reactor pressure at 0.15 MPa and theinternal temperature of the reactor at 40° C., the above-mentionedbenzene solution was injected in an amount of 6 ml, and stirring wascontinued for 0.3 hour. Further, while maintaining the internaltemperature of the reactor at 40° C., the above-mentioned benzenesolution was injected in an amount of 6 ml, and stirring was continuedfor 0.3 hour. The same operation was repeated seven times, and stirringwas continued for further 0.7 hour. The total amount of benzene injectedwas 0.595 g, and the total amount of R-113 injected was 57 ml. Further,nitrogen gas was supplied for 1.0 hour. The desired product wasquantified by ¹⁹F-NMR (internal standard: C₆F₆), whereby the yield ofthe above identified compound was 85%. The crude product was furtherdistilled to obtain 30 g of pure CF₂ClCFClCF(OCF₃)CF₂OCFClCF₂Cl.

¹⁹F-NMR (282.7 MHz, solvent: CDCl₃, standard: CFCl₃) δ (ppm); −52.4,−52.8 (3F), −60.7 to −64.2 (2F), −70.5 (2F), −76.5 (1F), −76.7 to −81.2(2F) −127.7, −128.5 (1F), −132.9, −133.7 (1F).

Boiling point: 35° C./0.5 kPa (absolute pressure)

Example 11 Preparation of CF₂═CFCF(OCF₃)CF₂OCF═CF₂

Into a three-necked flask made of glass, having an internal capacity of100 mL and equipped with a stirrer, a reflux condenser and a droppingfunnel, zinc (13 g, 200 mmol) was put, and 32 g of dimethyl formamidewas put. Then, the system was vacuumed to 27 kPa (absolute pressure),and further, the internal temperature was adjusted to from 65 to 70° C.CF₂ClCFClCF(OCF₃)CF₂OCFClCF₂Cl (12 g, 25 mmol) obtained in Example 10was slowly dropwise added thereto from the dropping funnel, and duringthe reaction, the product was distilled and quickly withdrawn.Thereafter, the crude product was fractionated to obtain pureCF₂═CFCF(OCF₃)CF₂OCF═CF₂ (4.0 g, yield: 47%).

¹⁹F-NMR (282.7 MHz, solvent: CDCl₃, standard: CFCl₃) δ (ppm); −55.4(F^(f), 3F) −86.5 (F^(h), 1F, J_(hi)=48 Hz), −87.0 to −88.6 (F^(d), 2F),−103.2 (F^(i), 1F, J_(gi)=116 Hz), −113.0 (F^(a), 1F, J_(ab)=83 Hz),−121.3 (F^(b), 1F, J_(bc)=111 Hz), −134.2 (F^(c), 1F, J_(ac)=65 Hz),−134.4 (F^(e), 1F), −184.0 (F^(g), 1F, J_(gh)=39 Hz). Here, a to i ofF^(a) to F^(i) correspond to the positions of the fluorine atoms shownin the following formula:

IR: 1785 cm⁻¹(CF₂═CF—), 1838 cm⁻¹(CF₂═CFO—).

Boiling point: 30° C./25.3 kPa (absolute pressure).

Example 12 Preparation of a Polymer by Polymerization ofCF₂═CFCF(OCF₃)CF₂OCF═CF₂

CF₂═CFCF(OCF₃)CF₂OCF═CF₂ (0.5 g) obtained in Example 11 andperfluorobenzoyl peroxide (1.5 mg) were put in a glass ampule, frozen inliquid nitrogen, vacuum deaerated and then sealed. The ampule was heatedin a warm water bath at 50° C. for 220 hours, whereupon the solidifiedcontent was taken out, and the remaining monomer was recovered undervacuum and then dried at 200° C. for 1 hour. The yield of the obtainedpolymer (hereinafter referred to as the polymer A1) was 43%. A part ofthe polymer A1 was dissolved in perfluoro(2-butyltetrahydrofuran)(hereinafter referred to as PBTHF), and the intrinsic viscosity wasmeasured and found to be 0.268 dl/g. The molecular weight of the polymerwas such that the number average molecular weight (M_(n)) was 102000,and the weight average molecular weight (M_(w)) was 201500.

The refractive index of the film of the polymer A₁ prepared by pressmolding was 1.334, and T_(g) was 113° C. The tensile characteristics ofthe polymer A1 were measured, whereby the tensile modulus was 1325 MPa,the yield stress was 35 MPa, and the breaking elongation was 3.9%.Further, the zero share viscosity at 230° C. was measured by a rotarymelt viscosity-measuring apparatus and found to be 5500 Pa·s. The glasstransition temperature, as measured by a differential scanningcalorimetry (DSC), of a polymer obtained by polymerizing monomerCF₂═CFCF₂CF₂OCF═CF₂ (hereinafter referred to as PBVE) under the sameconditions, was 108° C., whereby improvement of the glass transitiontemperature of the polymer A1 was confirmed.

Further, the infrared absorption spectrum of the polymer was measured,whereby absorption at 1785 cm⁻¹ attributable to CF₂═CF— and at 1838 cm⁻¹attributable to CF₂═CFO—, as observed with the monomer, was found tohave disappeared. This polymer A1 was found to have no pendant doublebond, be free from a crosslinking reaction, have a high conversion andbe completely soluble in R225 and thus found to be a cyclic polymer.Further, from the ¹⁹F-NMR analysis, it was confirmed to be a polymerhaving repeating units of the following structure. The polymer was foundto be excellent in transparency and useful as an optical resin materialfor e.g. an optical fiber or an optical waveguide.

Example 13 Preparation of Polymer A2

CF₂═CFCF(OCF₃)CF₂OCF═CF₂ (0.2 g) and diisopropyl peroxy dicarbonate (5mg) were put into a glass ampule, frozen in liquid nitrogen, vacuumdeaerated and then sealed. The ampule was heated in a warm water bath at40° C. for 20 hours, whereupon a solidified content was taken out anddried at 200° C. for 1 hour. The yield of the obtained polymer(hereinafter referred to as the polymer A2) was 95%. A part of thepolymer A2 was dissolved in PBTHF, and the intrinsic viscosity wasmeasured and found to be 0.09 dl/g.

Example 14 Preparation of Polymer A3

Into an autoclave made of stainless steel and having an internalcapacity of 200 mL, water (80 g), CF₂═CFCF(OCF₃)CF₂OCF═CF₂ (15 g, 43.6mmol) and perfluorobenzoyl peroxide (38 mg) were charged. The autoclavewas flushed with nitrogen and then heated until the internal temperatureof the autoclave became 70° C., followed by polymerization for 20 hours.The obtained polymer was washed with deionized water and methanol, andthen dried at 200° C. for 1 hour. The yield of the obtained polymer(hereinafter referred to as the polymer A3) was 70%.

A part of the polymer A3 was dissolved in PBTHF, and the intrinsicviscosity was measured and found to be 0.25 dl/g. The refractive indexof a film of the polymer A3 prepared by press molding was 1.334, andT_(g) was 113° C. The tensile characteristics of the polymer A3 weremeasured, whereby the tensile modulus was 1330 MPa, the yield stress was35 MPa, and the breaking elongation was 3.5%. Further, the zero shareviscosity at 230° C. was measured by a rotary meltviscoelasticity-measuring apparatus and found to be 5300 Pa·s.

Example 15 Preparation of Polymer B1 by Copolymerization ofCF₂═CFCF(OCF₃)CF₂OCF═CF₂ with Tetrafluoroethylene

Into a 200 mL autoclave made of stainless steel, R225 (80 mL),CF₂═CFCF(OCF₃)CF₂OCF═CF₂ (5.6 g, 16.3 mmol) and perfluorobenzoicperoxide (25 mg) were charged. While cooling the autoclave with liquidnitrogen, it was vacuumed by a vacuum pump, and the vacuum pump wasdetached, and the temperature was returned to room temperature, andthen, again, while cooling with liquid nitrogen, it was vacuumed by avacuum pump. This operation was repeated three times. Then, the internaltemperature of the autoclave was returned to room temperature, whereupontetrafluoroethylene (32 g, 320 mmol) was introduced. And, heating wascarried out until the internal temperature became 70° C., followed bypolymerization for 3 hours. Thereafter, the remainingtetrafluoroethylene was purged, and the remaining monomer was distilledoff under reduced pressure, to obtain 29 g of a white polymer(hereinafter referred to as the polymer B1). The structure of thepolymer B1 was analyzed, whereby it was found to be a polymer having astructure derived from CF₂═CFCF(OCF₃)CF₂OCF═CF₂ introduced in an amountof 1.4 mol % to a part of polytetrafluoroethylene.

T_(g) of the polymer B1 was 130° C.

Example 16 Preparation of Polymer B2 by Copolymerization ofCF₂═CFCF(OCF₃)CF₂OCF═CF₂ with PBVE

Into an autoclave made of stainless steel and having an internalcapacity of 200 mL, water (80 g), CF₂═CFCF(OCF₃)CF₂OCF═CF₂ (15 g), PBVE(15 g), perfluorobenzoyl peroxide (75 mg) and methanol (1.5 g) werecharged. The autoclave was flushed with nitrogen and then heated untilthe internal temperature of the autoclave became 70° C., followed bypolymerization for 20 hours. The obtained polymer (hereinafter referredto as the polymer B2) was washed with deionized water and methanol andthen dried at 200° C. for 1 hour. The yield of the obtained polymer B2was 80%.

A part of the polymer B2 was dissolved in PBTHF, and the intrinsicviscosity was measured and found to be 0.33 dl/g. the refractive indexof a film of the polymer B2 prepared by press molding was 1.338, andT_(g) was 110° C.

Example 17 Preparation of Polymer B3 by Copolymerization ofCF₂═CFCF(OCF₃)CF₂OCF═CF₂ with Perfluoro(2,2-Dimethyl-1,3-Dioxol)(Hereinafter Referred to as PDD)

Into an autoclave made of stainless steel and having an internalcapacity of 200 mL, water (80 g), CF₂═CFCF(OCF₃)CF₂OCF═CF₂ (21 g), PDD(9 g), diisopropyl peroxy dicarbonate (75 mg) and methanol (1.5 g) werecharged. The autoclave was flushed with nitrogen and then heated untilthe internal temperature of the autoclave became 40° C., followed bypolymerization for 20 hours. The obtained polymer (hereinafter referredto as the polymer B3) was washed with deionized water and methanol andthen dried at 200° C. for 1 hour. The yield of the obtained polymer B3was 90%.

A part of the polymer B3 was dissolved in PBTHF, and the intrinsicviscosity was measured and found to be 0.36 dl/g. The refractive indexof a film of the polymer B3 prepared by press molding, was 1.320, andT_(g) was 158° C.

Example 18 Preparation of Optical Fiber

The polymer A3 (93 parts) obtained in Example 14 andperfluoro(triphenyltriazine) (7 parts) were put into a glass ampule, andafter sealing, uniformly melt-mixed at 240° C. to obtain a polymermixture (hereinafter referred to as the mixture C1). The refractiveindex of a film of the mixture C1 prepared by press molding, was 1.354,and Tg was 93° C.

Then, in accordance with the method disclosed in JP-A-8-5848, an opticalfiber was prepared by using the mixture C1 and the polymer A3. Namely,firstly, the mixture C1 was melted in a sealed glass tube to obtain acolumnar molded product (C1 a). Then, the polymer A3 alone wasmelt-molded into a cylinder, and while inserting the molded product (C1a) into the hollow portion of this cylinder, the temperature was raisedto 240° C. to join them to obtain a preform. This preform was melt-spunat 240° C. to obtain an optical fiber wherein the refractive indexgradually decreases from the center portion towards the peripheralportion.

The optical transmission loss of the obtained optical fiber was measuredby a cutback method, whereby it was 195 dB/km at 650 nm, 1.10 dB/km at850 nm and 83 dB/km at 1300 nm, and it was an optical fiber capable oftransmitting light from a visible light to a near infrared lightexcellently.

This optical fiber was heated and stored in an oven of 70° C. for 1000hours and then withdrawn, whereupon the refractive index distributionwas measured by an interface interference microscope and compared withthe refractive index distribution before the heating and storing,whereby no change was observed. Further, the transmission band wasmeasured by a pulse method to evaluate the transmission characteristics.The optical fiber was heated and stored at 70° C. for 1000 hours,whereupon the transmission band was measured, whereby it was 350 MHz·kmboth before and after the heating and storing, and no decrease of theband was observed, and thus it was confirmed that the heat resistancewas excellent.

Example 19 Preparation of an Optical Fiber

By means of an extruder, dichroic extrusion was carried out so that apolymer of PBVE (intrinsic viscosity: 0.27 dl/g, refractive index:1.342) was disposed at the center and the polymer A3 was disposed at thecircumferential portion concentrically, thereby to spin a core/cladoptical fiber. The obtained optical fiber had an outer diameter of 520μm and a core diameter of 485 μm. Further, the optical transmission losswas measured by a cutback method, whereby it was 148 dB/km at 650 nm, 88dB/km at 850 nm and 73 dB/km at 1300 nm, and thus, it was an opticalfiber capable of transmitting light from a visible light to a nearinfrared light excellently.

Example 20 Preparation of an Optical Fiber

A hollow tube made of the polymer B3 was put on the preform obtained inExample 18, followed by melt spinning at 240° C. to obtain an opticalfiber wherein the refractive index gradually decreases from the centerportion towards the peripheral portion. The optical transmission loss ofthe obtained optical fiber was measured by a cutback method, whereby itwas 143 dB/km at 650 nm, 61 dB/km at 850 nm and 35 dB/km at 1300 nm, andit was confirmed to be an optical fiber capable of transmitting lightfrom a visible light to a near infrared light excellently. Further, theincrease of the loss at a bending radius of 10 mm of this optical fiberwas measured at 850 nm and found to be 0.14 dB, and thus, it was foundto be an optical fiber having a small bending loss.

This optical fiber was heated and stored in an oven of 70° C. for 1000hours, whereupon the transmission loss was measured, whereby no changewas observed. Further, the transmission band was measured by a pulsemethod to evaluate the transmission characteristics. The transmissionband was measured after heating and storing the optical fiber at 70° C.for 1000 hours, whereby it was 275 MHz·km both before and after theheating and storing, and no decrease of the band was observed, and thusit was confirmed that the heat resistance was excellent.

Example 21 Preparation of Polymer D1

PDD and tetrafluoroethylene were subjected to radical polymerization ina mass ratio of 80:20 by using PBTHF as a solvent, to obtain a polymerwhich has T_(g) of 160° C. and M_(n) of 1.7×10⁵. This polymer wassubjected to heat treatment at 250° C. for 5 hours in an atmosphere of afluorine/nitrogen mixed gas (fluorine gas concentration: 20 vol%), toobtain a polymer (hereinafter referred to as the polymer D₁) having goodlight transmittance and thermal stability. The polymer D1 was colorlesstransparent, and the refractive index was 1.305.

Example 22 Preparation of an Optical Fiber

By means of an extruder, dichroic extrusion was carried out so that thepolymer A3 was disposed at the center portion and the polymer D1 wasdisposed at the circumferential portion concentrically, to spin anoptical fiber of core/clad type. The obtained optical fiber had an outerdiameter of 990 μm and a core diameter of 905 μm. Further, the opticaltransmission loss was measured by a cutback method, whereby it was 189dB/km at 650 nm, 98 dB/km at 850 nm, and 75 dB/km at 1300 nm, and thusit was an optical fiber capable of transmitting light from a visiblelight to a near infrared light excellently.

Example 23 Preparation of an Optical Fiber

92.5 parts of the polymer A3 and 7.5 parts ofperfluoro(1,3,5-triphenylbenzene) were put into a glass ampule, sealedand uniformly melt-mixed at 250° C. to obtain a polymer mixture(hereinafter referred to as the mixture C2). The refractive index of afilm made of the mixture C2 prepared by press molding, was 1.350, andT_(g) was 95° C.

Then, an optical fiber was prepared by using the mixture C2 and thepolymer A3. Namely, firstly, the mixture C2 was melted in a glass sealedtube to obtain a columnar molded product C2a. Then, a cylinder wasmelt-molded solely by the polymer A3, and while inserting the moldedproduct C2a in the hollow portion of this cylinder, heating was carriedout at 220° C. to join them to obtain a preform. This preform wasmelt-spun at 240° C. to obtain an optical fiber wherein the refractiveindex gradually decreases from the center portion towards the peripheralportion.

The optical transmission loss of the obtained optical fiber was measuredby a cutback method. Whereby it was 185 dB/km at 650 nm, 96 dB/km at 850nm, and 82 dB/km at 1300 nm, and thus, it was an optical fiber capableof transmitting light from a visible light to a near infrared lightexcellently.

This optical fiber was heated and stored in an oven of 70° C. for 2000hours, and then taken out, whereupon the refractive index distributionwas measured by an interface interference microscope, and compared withthe refractive index distribution before the heating and storing,whereby no change was observed. Further, the transmissioncharacteristics were evaluated by measuring the transmission band by apulse method. The optical fiber was heated and stored at 70° C. for 2000hours, whereupon the transmission band was measured, whereby it was 335MHz·km both before and after the heating and storing, and no decrease ofthe band takes place, and it was confirmed that the heat resistance wasgood.

Example 24 Preparation of an Optical Fiber

90 parts of the polymer A3 and 10 parts of chlorotrifluoroethyleneoligomer were put into a glass ampule and, after sealing, uniformlymelt-mixed at 250° C. to obtain a polymer mixture (hereinafter referredto as the mixture C3). The refractive index of a film of the mixture C3prepared by press molding was 1.345, and T_(g) was 84° C.

Then, an optical fiber was prepared by using the mixture C3 and thepolymer A3. Namely, firstly, the mixture C3 was melted in a sealed glasstube to obtain a columnar molded product C3a. Then, the polymer A3 alonewas melt-molded into a cylinder, and while inserting the molded productC3a into the hollow portion of this cylinder, heating at 220° C. wascarried out to join them to obtain a preform. This preform was melt-spunat 240° C. to obtain an optical fiber wherein the refractive indexgradually decreases from the center portion towards the peripheralportion.

The optical transmission loss of the obtained optical fiber was measuredby a cutback method, whereby it was 125 dB/km at 650 nm, 71 dB/km at 850nm, and 53 dB/km at 1300 nm, and thus, it was an optical fiber capableof transmitting light from a visible light to a near infrared lightexcellently.

This optical fiber was heated and stored in an oven of 70° C. for 1000hours and then, withdrawn, whereupon the refractive index distributionwas measured by an interfaco interference microscope and compared withthe refractive index distribution prior to the heating and storing,whereby no change was observed. Further, the transmissioncharacteristics were evaluated by measuring the transmission band by apulse method. The transmission band was measured after heating andstoring the optical fiber at 70° C. for 1000 hours, whereby it was 328MHz·km both before and after the heating and storing, and no decrease ofthe transmission band was observed, whereby it was confirmed that theheat resistance was excellent.

INDUSTRIAL APPLICABILITY

According to the present invention, a novel fluoropolymer which can bean optical resin material having a low refractive index, excellent heatresistance and a high glass transition temperature as compared with aconventional polymer of a fluorinated diene having no side chain, and anovel fluorinated diene compound having two unsaturated bonds, capableof presenting such a fluoropolymer, can be provided. Further, bydissolving the fluoropolymer in a certain specific fluorocarbon solvent,it is possible to provide a useful fluoropolymer solution. Further, thefluoropolymer has a low refractive index and excellent heat resistance,whereby a high performance optical transmitter and a plastic opticalfiber can be provided.

The entire disclosure of Japanese Patent Application No. 2001-334352filed on Oct. 31, 2001 including specification, claims and summary isincorporated herein by reference in its entirety.

1. A fluorinated diene compound represented by the following formula(1):CF₂═CFCF(OR^(f))CF₂OCF═CF₂  (1) wherein R^(f) is a perfluoroalkyl group.2. The fluorinated diene compound according to claim 1, wherein R^(f) isa trifluoromethyl group.
 3. A method for producing a fluorinated dienecompound represented by the following formula (1), characterized in thata dehalogenation reaction is carried out at halogen atoms other thanfluorine atoms in at least one compound selected from a compoundrepresented by the following formula (2) and a compound represented bythe following formula (3):CF₂═CFCF(OR^(f))CF₂OCF═CF₂  (1)CF₂Z¹CFZ²CF(OR^(f))CF₂OCF═CF₂  (2)CF₂Z¹CFZ²CF(OR^(f))CF₂OCFZ³CF₂Z⁴  (3) wherein R^(f) is a perfluoroalkylgroup, and each of Z¹, Z², Z³ and Z⁴ which are independent of oneanother, is a halogen atom other than a fluorine atom.
 4. Afluoropolymer comprising monomer units formed by cyclopolymerization ofa fluorinated diene compound represented by the formula (1), or monomerunits formed by cyclopolymerization of a fluorinated diene compoundrepresented by the formula (1) and monomer units formed bypolymerization of other monomer polymerizable with the fluorinated dienecompound represented by the formula (1):CF₂═CFCF(OR^(f))CF₂OCF═CF₂  (1) wherein R^(f) is a perfluoroalkyl group.5. The fluoropolymer according to claim 4, wherein R^(f) is atrifluoromethyl group.
 6. The fluoropolymer according to claim 4,wherein the monomer units formed by the cyclopolymerization of thefluorinated diene monomer represented by the formula (1), are monomerunits represented by any one of the following formulae, wherein R^(f) isas defined above:


7. The fluoropolymer according to claim 4, wherein the monomer units ofother polymerizable monomer are monomer units formed by polymerizationof at least one member selected from a fluorinated diene which iscyclopolymerizable, other than the fluorinated diene compoundrepresented by the formula (1), a monomer having a fluorinated aliphaticcyclic structure, a fluorinated non-cyclic vinyl ether monomer and afluoroolefin.
 8. The fluoropolymer according to claim 4, wherein theother monomer units are monomer units formed by polymerization of atleast one member selected from tetrafluoroethylene, perfluoro(butenylvinyl ether) and perfluoro(2,2-dimethyl-1,3-dioxole).
 9. A fluoropolymersolution having the fluoropolymer as defined in claim 4 dissolved in atleast one fluorocarbon solvent selected fromperfluoro(2-butyltetrahydrofuran), perfluorooctane, perfluorohexane,perfluoro(tributylamine), perfluoro(tripropylamine), perfluorobenzeneand dichloropentafluoropropane.
 10. An optical transmitter made by usingthe fluoropolymer as defined in claim
 4. 11. A plastic optical fiberhaving a core formed of a mixture comprising the fluoropolymer asdefined in claim 4 and a fluorinated low molecular compound as arefractive index-increasing agent.
 12. The plastic optical fiberaccording to claim 11, wherein the fluorinated low molecular compound isat least one compound selected from perfluoro(triphenyltriazine),perfluoro(1,3,5-triphenylbenzene) and a chlorotrifluoroethyleneoligomer.
 13. The plastic optical fiber according to claim 11, whereinthe plastic optical fiber is a refractive index distribution typeoptical fiber.